Advancing to the place of danger, and entering within the fouled air, his lighted lamp in hand, Stephenson held it finally out, in the full current of the blower, and within a few inches of its mouth. Thus exposed, the flame of the lamp at first increased, then flickered, and then went out; but there was no explosion of the gas. Returning to his companions, who were still at a distance, he told them what had occurred. Having now acquired somewhat more confidence, they advanced with him to a point from which they could observe him repeat his experiment, but still at a safe distance. They saw that when the lighted lamp was held within the explosive mixture, there was a great flame; the lamp became almost full of fire; and then it smothered out. Again returning to his companions, he relighted the lamp, and repeated the experiment several times with the same result. At length Wood and Moodie ventured to advance close to the fouled part of the pit; and, in making some of the later trials, Mr. Wood himself held up the lighted lamp to the blower. Before leaving the pit, Stephenson expressed his opinion that by an alteration of the lamp which he then contemplated, he could make it burn better; this was by a change in the slide through which the air was admitted into the lower part, under the flame. After making some experiments on the air collected at the blower, by bladders which were mounted with tubes of various diameters, he satisfied himself that, when the tube was reduced to a certain diameter, the foul air would not pass through; and he fashioned his slide accordingly, reducing the diameter of the tube until he conceived it was quite safe. In about a fortnight the experiments were repeated, in a place purposely made foul as before; on this occasion a larger number of persons ventured to witness them, and they again proved successful. The lamp was not yet, however, so efficient as the inventor desired. It required, he observed, to be kept very steady when burning in the inflammable gas, otherwise it was liable to go out, in consequence, as he imagined, of the contact of the burnt air (as he then called it), or azotic gas, which lodged round the exterior of the flame. If the lamp was moved horizontally, the azote came in contact with the flame and extinguished it. “It struck me,” said he, “that if I put more tubes in, I should discharge the poisonous matter that hung round the flame, by admitting the air to its exterior part.” Although he had then no access to scientific books, nor intercourse with scientific men, nor anything that could assist him in his investigation, besides his own indefatigable spirit of inquiry, he contrived a rude apparatus by which he tested the explosive properties of the gas and the velocity of current (for this was the direction of his inquiries) necessary to enable the explosive gas to pass through tubes of different diameters. In making these experiments in his humble cottage at the West